feat(isVAT): add validation for Colombian nit

[jorgevrgs]

feat(validatorName): add validation for Colombian nit

See: https://es.wikipedia.org/wiki/N%C3%BAmero_de_Identificaci%C3%B3n_Tributaria_(Colombia)

Checklist

• PR contains only changes related; no stray files, etc.
• README updated (where applicable)
• Tests written (where applicable)
• References provided in PR (where applicable)

[codecov]

Codecov Report

❌ Patch coverage is 87.50000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 99.96%. Comparing base (6f436be) to head (ae9b131).

Files with missing lines	Patch %	Lines
src/lib/isVAT.js	87.50%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##            master    #2597      +/-   ##
===========================================
- Coverage   100.00%   99.96%   -0.04%     
===========================================
  Files          114      114              
  Lines         2536     2543       +7     
  Branches       642      644       +2     
===========================================
+ Hits          2536     2542       +6     
- Partials         0        1       +1     

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